Communication control device, transmission power allocation method and program

ABSTRACT

There is provided a doing apparatus including a communication control device including a power allocation unit configured to allocate transmission power for secondary use of a frequency channel protected for a primary system to a secondary system. The power allocation unit switches power allocation methods between a first group of secondary systems of which a distance from the primary system is less than a prescribed threshold and a second group of secondary systems of which a distance from the primary system exceeds the prescribed threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/422,098, filed on Feb. 1, 2017, which is a continuation ofU.S. patent application Ser. No. 14/372,329 filed Jul. 15, 2014, issuedas U.S. Pat. No. 9,596,657 on Mar. 14, 2017, which application is anational phase entry under 35 U.S.C. § 371 of International ApplicationNo. PCT/JP2012/080737, filed on Nov. 28, 2012, published on Aug. 1, 2013as WO 2013/111442, which claims the benefit of Japanese PatentApplication No. 2012-011736 filed Jan. 24, 2012, the disclosures ofwhich are hereby incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a communication control device, atransmission power allocation method and program.

BACKGROUND ART

Secondary usage of a frequency is discussed as a measure for alleviatingfuture depletion of frequency resources. The secondary usage of afrequency means that part of or all the frequency channelspreferentially allocated for a system is secondarily used by the othersystem. Typically, a system which is preferentially allocated with afrequency channel is called a primary system and a system whichsecondarily uses the frequency channel is called a secondary system.

A TV white space is an exemplary frequency channel whose secondary usageis discussed (see Non-Patent Literature 1). The TV white space is achannel which is not used by a TV broadcast system depending on an areaamong frequency channels allocated for the TV broadcast system as aprimary system. The TV white space is opened to a secondary system sothat efficient utilization of the frequency resource is to be achieved.A standard for a physical layer (PHY) and a MAC layer for enabling thesecondary usage of the TV white space can include IEEE802.22,IEEE802.11af and ECMA (European Computer Manufacturer Association)-392(CogNea, see Non-Patent Literature 2 described later).

In the secondary usage of a frequency band, in general, the secondarysystem is required to be operated so as not to give a detrimentalinterference to the primary system. In order to do so, one of theimportant technologies is transmission power control. For example,Patent Literatures 1 described later proposes an approach to determinethe maximum transmission power of a secondary system in response to apath loss of a path between the base station of the secondary system andthe receiver device of the primary system.

CITATION LIST Non-Patent Literature

Non-Patent Literature 1: Electronic Communications Committee (ECC)within the European Conference of Postal and TelecommunicationsAdministrations (CEPT), “TECHNICAL AND OPERATIONAL REQUIREMENTS FOR THEPOSSIBLE OPERATION OF COGNITIVE RADIO SYSTEMS IN THE ‘WHITE SPACES’ OFTHE FREQUENCY BAND 470-790 MHz”, ECC REPORT 159, Cardiff, January 2011.

Non-Patent Literature 2: “Standard ECMA-392 MAC and PHY for Operation inTV White Space”, [online], [retrieved on Dec. 15, 2011], the Internet<URL:http://www.ecma-internationatorg/publications/standards/Ecma-392.htm>

PATENT LITERATURE

Patent Literature 1: JP2009-100452A

SUMMARY OF INVENTION Technical Problem

In the situation in which plural secondary systems can possibly bepresent, it would be beneficial to control the transmission power ofeach secondary system so that accumulative interferences from the pluralsecondary systems fall within an acceptable range of the primary system.In addition, when the transmission power of the secondary systems is notsmall, consideration of interference between channels may possiblybecome necessary. However, in order to accurately evaluate such variousfactors for all of the secondary systems, calculation cost forallocating the transmission power will increase, and extra load will beimposed on a control node controlling the secondary use.

Accordingly, it is desirable that a system be provided that suppressesthe load to calculate the transmission power of the secondary systemsand that appropriately prevents detrimental interference to the primarysystem.

Solution to Problem

According to the present invention, there is provided a doing apparatusincluding a communication control device including a power allocationunit configured to allocate transmission power for secondary use of afrequency channel protected for a primary system to a secondary system.The power allocation unit switches power allocation methods between afirst group of secondary systems of which a distance from the primarysystem is less than a prescribed threshold and a second group ofsecondary systems of which a distance from the primary system exceedsthe prescribed threshold.

In addition, according to the present invention, there is provided amethod for allocating transmission power for secondary use of afrequency channel protected for a primary system to a secondary system,the method including obtaining a distance to the secondary system fromthe primary system, allocating transmission power to the secondarysystem with the first power allocation method when the obtained distanceis less than a prescribed threshold, and allocating transmission powerto the secondary system with the second power allocation method thatrequires calculation cost lower than that of the first power allocationmethod when the obtained distance exceeds the prescribed threshold.

In addition, according to the present invention, there is provided aprogram for causing a computer of a communication control device tofunction as a power allocation unit to allocate transmission power forsecondary use of a frequency channel protected for a primary system to asecondary system. The power allocation unit switches power allocationmethods between a first group of secondary systems of which a distancefrom the primary system is less than a prescribed threshold and a secondgroup of secondary systems of which a distance from the primary systemexceeds the prescribed threshold.

Advantageous Effects of Invention

According to the technology related to the present disclosure, it ispossible to suppress load to calculate transmission power of thesecondary systems and to appropriately prevent detrimental interferenceto the primary system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram for explaining an interference a nodeof a primary system suffers upon secondary usage of a frequency.

FIG. 2 is an explanatory diagram for explaining an interference in achannel and an interference between channels.

FIG. 3 is an explanatory diagram for explaining a configuration of acommunication control system according to one embodiment.

FIG. 4 is a sequence diagram illustrating an exemplary schematic flow ofa communication control processing performed in the communicationcontrol system according to one embodiment.

FIG. 5 is a block diagram illustrating an exemplary configuration of thecommunication control device according to one embodiment.

FIG. 6 is a flowchart illustrating an exemplary flow of a powerallocation process according to one embodiment.

FIG. 7 is a block diagram illustrating of an exemplary configuration ofa master node of the secondary system according to one embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

A description will be given in the following order.

1. Outline of system

2. Exemplary configuration of secondary system manager

2-1. Explanation of units

2-2. Flow of process

3. Exemplary configuration of master node

4. Conclusion

1. OUTLINE OF SYSTEM

First, with reference to FIG. 1 to FIG. 4, a description will be givenof an outline of a communication control system according to anembodiment.

[1-1. Problem Relating to One Embodiment]

FIG. 1 is an explanatory diagram for explaining an interference a nodeof a primary system suffers upon secondary usage of a frequency. Withreference to FIG. 1, there are illustrated a primary transmissionstation 10 for providing services of the primary system, and a primaryreception station 20 located inside a boundary 12 of a service area forthe primary system. The primary transmission station 10 may be a TVbroadcast station, or a wireless base station or repeater station in acellular communication system, for example. The cellular communicationsystem may include the GSM, UMTS, WCDMA, CDMA2000, LTE, LTE-Advanced,IEEE802.16, WiMAX or WiMAX2, and the like. When the primary transmissionstation 10 is a TV broadcast station, the primary reception station 20is a receiver having an antenna and a tuner for receiving TV broadcast.When the primary transmission station 10 is a wireless base station in acellular communication system, the primary reception station 20 is awireless terminal operating in accordance with the cellularcommunication system. In the example of FIG. 1, a channel F1 isallocated for the primary transmission station 10. The primarytransmission station 10 can provide TV broadcast services, wirelesscommunication services or some other wireless services by transmittingwireless signals on the channel F1. Note that the embodiment is notlimited to the example in FIG. 1, but plural frequency channels can beallocated for the primary system.

FIG. 1 further shows master nodes 200 a, 200 b, 200 c, and 200 d eachoperating the secondary system. Each of the master nodes uses thechannel F1 allocated for the primary system or an adjacent channel F2 orF3 to operate the secondary system respectively. Each master node may bea wireless access point which is compliant with or partially uses awireless communication system such as IEEE802.22, IEEE802.11, or ECMA,or may be a wireless base station or repeater station which is compliantwith the cellular communication system or partially uses standardsthereof. If the secondary system is operated in accordance with thecellular communication system, the cellular communication system may bethe same as or different from a system of the primary system. One ormore slave nodes (not shown) for the secondary system may exist aroundeach master node. Slave nodes support the same wireless communicationsystem as the master node which they are connected to. In the example ofFIG. 1, a master node 200 a located outside a boundary 14 of a guardarea uses the channel F1. Master nodes 200 b and 200 c located insidethe guard area use the channels F2 and F3, respectively, adjacent to thechannel F1. A master node 200 d located outside the boundary 14 of theguard area uses the channel F2.

Under the circumstances such as of FIG. 1, the primary reception station20 may be influenced by an interference due to the wireless signalstransmitted from secondary transmission stations (both master node andslave node). FIG. 2 is an explanatory diagram for explaining aninterference in channel (in-band) and an interference between channels.In the example of FIG. 2, the channel F1 is a channel used by theprimary system. If the master node 200 a in FIG. 1 secondarily uses thischannel F1, an interference may occur in the same channel. The channelF2 is a channel adjacent to the channel F1. The channel F3 is a channeladjacent to the channel F2. A guard band is provided between the channelF1 and the channel F2, and between the channel F2 and the channel F3.When these channels F2 and F3 are used by other system, the primarysystem is ideally to suffer no interference. However, as illustrated inFIG. 2, actually a considerable interference may occur from an adjacentchannel (such as channels F2, F3 and other channels) due to out-bandradiation.

The transmission power of the secondary system can be controlled in thesystem exemplified in FIG. 3 so as not to give a detrimental effect onthe primary system that should be protected from this interference dueto the wireless signals from secondary system.

FIG. 3 is an explanatory diagram for explaining a communication controlsystem 1 according to one embodiment. With reference to FIG. 3, thecommunication control system 1 includes a primary transmission station10, data server 30, communication control device 100, and master nodes200 a and 200 b. Here, in the example of FIG. 3, only the master nodes200 a and 200 b are illustrated as a master node operating the secondarysystem, but actually more master nodes may exist. Unless otherwise themaster nodes 200 a and 200 b (and other master nodes) need to bedistinguished from each other in the explanation of this descriptionbelow, an alphabetical character suffixed to a symbol is omitted tocollectively refer to these as the master node 200.

The data server 30 is a server device having a database storing thereindata about the secondary usage. The data server 30 accepts an accessfrom the master node 200 to provide data indicating secondarily usablechannels and position data of the transmission station 10 of the primarysystem to the master node 200. Additionally, the master node 200registers information on the secondary system in the data server 30 atthe start of the secondary usage. Communication between the data server30 and the master node 200 may be made via an arbitrary network such asthe Internet. Refer to Non-Patent Literature 1 describing the secondaryusage of the TV white space as to an exemplary specification of the dataserver like this.

The communication control device 100 has a function as a secondarysystem manager which allocates the transmission power for the secondaryusage of the frequency channel to the secondary system such that theaccumulative interferences from a secondary system give no detrimentaleffect to primary system. The communication control device 100 canaccess to the data server 30 via a network such as the Internet, forexample, and acquires data used for allocating the transmission powerfrom the data server 30. In addition, the communication control device100 is communicably connected with also each master node 200. Then thecommunication control device 100, in response to a request from themaster node 200 or primary system, or periodically, adjusts thetransmission power for the secondary system. Note that, without limitedto the example of FIG. 3, the communication control device 100 may bemounted on the physically same device as the data server 30 or any ofthe master nodes 200.

FIG. 4 is a sequence diagram illustrating an exemplary schematic flow ofan communication control processing performed in the communicationcontrol system 1.

First, the master node 200, before starting to operate the secondarysystem, registers information on the secondary system in the data server30 (step S10). The information registered here may include, for example,a device ID, class and position data of the master node 200 and thelike. Moreover, in response to registration of the information on thesecondary system, the data server 30 notifies the master node 200 ofinformation for configuring the secondary system such as a list ofchannel numbers of secondarily usable frequency channels, acceptablemaximum transmission power, and spectrum mask. Here, an access cyclefrom the master node 200 to the data server 30 may be decided on thebasis of provisions of law regarding frequency usage regulation. Forexample, the FCC (Federal Communications Commission) is considering arequirement that if the position of the master node varies, the positiondata should be updated at least every 60 seconds. In addition, it hasbeen recommended that the list of the usable channel numbers should bechecked by the master node at least every 30 seconds. However, increasein the access to the data server 30 leads to increase in overhead.Therefore, the access cycle to the data server 30 may be set to a longercycle (e.g., integral multiple of the regulated cycle and so on).Moreover, the access cycle may be dynamically set depending on thenumber of active nodes (e.g., if the number of nodes is small, a risk ofinterference is low so that the cycle may be set longer). The dataserver 30 may instruct the master node 200 about the access cycle uponan initial registration of the information on the secondary system, forexample.

Further, the communication control device 100 receives information onthe primary system from the data server 30 periodically, for example,and uses the received information to update information stored in itself(step S11). The information received here may include one or more of theposition data of the primary transmission station 10, height of anantenna, width of the guard area, list of the channel numbers of thefrequency channels, acceptable interference amount of the primarysystem, position data of a reference point for interference calculationdescribed later, list of IDs of the registered master nodes 200, andother parameters (e.g., ACLR (adjacent channel leakage ratio), fadingmargin, shadowing margin, protection ratio, ACS (adjacent channelselection) and the like). Here, the communication control device 100 mayindirectly receive all or a part of the information on the primarysystem (e.g., list of the channel numbers and the like) from the masternode 200.

Next, the master node 200 configures the secondary system on the basisof the information notified by the data server 30 (step S12). Forexample, the master node 200 selects one or more channels from thesecondarily usable frequency channels as a use channel for the secondarysystem. Then, a request for power allocation is transmitted from themaster node 200 (or the data server 30) to the communication controldevice 100 (step S13).

When an acknowledge is returned to the request for power allocation,mutual authentication and application level information exchange areperformed between the communication control device 100 and the masternode 200 (step S14). Additionally, the information on the secondarysystem is transmitted from the master node 200 to the communicationcontrol device 100 (step S15). The information transmitted here mayinclude a device ID of the master node 200, class, position data,channel number of the frequency channel (use channel) selected by themaster node 200, information on a communication quality requirement(including a QoS (Quality of Service) requirement), priorityinformation, communication history and the like.

Next, the communication control device 100 performs a power allocationprocessing on the basis of the information acquired from the data server30 and the master node 200 (step S16). The power allocation processinghere by the communication control device 100 will be described in detaillater. Then, the communication control device 100 transmits a powernotification message for notifying a newly allocated transmission powerto the master node 200 (step S17).

The master node 200, in receiving the power notification message, setsan output level of a transmitting circuit in itself in accordance with avalue of the notified transmission power (step S18). Further, the masternode 200 may instruct a slave node connected with itself about a valueof the transmission power to be used. The master node 200, in completingthe setting of the transmission power, reports the secondary systemconfiguration to the communication control device 100 (step S19). Then,the communication control device 100 updates the information onsecondary system stored in itself in response to the report from themaster node 200 (step S20).

In the above-described sequence, in the power allocation processingperformed by the communication control device 100 in step S16, there aresome aspects to be considered in accordance with the situations.

The first aspect is a path loss for each secondary system. In general,the greater the path-loss from a secondary system to a primary systemis, the lower the interference level that the primary system receivesbecomes. Consequently, by allocating greater transmission power to asecondary system located farther away from the primary system,throughput of the secondary system can be enhanced. However, becausethere is an upper limit to the transmission power that can be outputfrom the nodes of the secondary system (both master node and slavenode), when the distance of the secondary system from the primary systemexceeds a certain value, it is no longer significant to consider thepath loss.

The second aspect is accumulative interferences from plural secondarysystems to a primary system. Generally, in order to appropriatelyprotect the primary system, when plural secondary systems are present,it is desirable that the transmission power is controlled so that theaccumulative interferences from these plural secondary systems give nodetrimental effect to the primary system. However, calculation ofaccumulative interferences of secondary systems having an interferencelevel sufficiently smaller than the acceptable interference level of theprimary system brings a disadvantage of increase in calculation load.

The third aspect is the interference between channels. Generally, inorder to appropriately protect a primary system, it is desirable thatthe transmission power is controlled so that the interference from thesecondary system gives no detrimental effect to the primary system afterthe interference between channels is properly evaluated. However, whenonly an interference on the same channel is considered, simplecalculation of the transmission power can be made independently for eachchannel, whereas when the interference between channels is considered,the transmission power needs to be distributed in a comprehensiblemanner over the plural secondary systems that secondarily use channelsdifferent from one another. Because when the number of channelsincreases, combinations of channels that may cause the interferencebetween channels also increase, such calculation load becomessignificantly large. Accordingly, it is a beneficial option not toconsider the interference between channels for the secondary systemswith a small interference level.

In view of the above, the communication control device 100, whenallocating the transmission power to a secondary system, prevents adetrimental effect on the primary system while suppressing calculationload by switching power allocation methods in accordance with thedistance of the secondary system from the primary system.

2. EXEMPLARY CONFIGURATION OF SECONDARY SYSTEM MANAGER

FIG. 5 is a block diagram illustrating an example of the configurationof the communication control device 100 (i.e., the secondary systemmanager) illustrated in FIG. 3. With reference to FIG. 5, thecommunication control device 100 is provided with a communication unit110, a storage unit 120 and a control unit 130. The control unit 130includes a power allocation unit 140.

[2-1. Explanation of Units]

The communication unit 110 is a communication interface forcommunication of the communication control device 100 with the dataserver 30 and with the master node 200. Communication between thecommunication control device 100 and the data server 30, and between thecommunication control device 100 and the master node 200 may be achievedby any of a wired communication or wireless communication, or acombination thereof.

The storage unit 120 stores a program and data for operation for thecommunication control device 100 using a storage medium such as a harddisk or semiconductor memory. For example, the storage unit 120 storesthe information on the primary system received from the data server 30and the information on the secondary system received from the masternode 200 of each secondary system.

The control unit 130 corresponds to a processor such as CPU (CentralProcessing Unit) or DSP (Digital Signal Processor). The control unit 130causes various functions of the communication control device 100 byexecuting programs stored in the storage unit 120 or other storagemedia.

The power allocation unit 140 allocates for the secondary system thetransmission power for the secondary usage of a frequency channelprotected for the primary system. The frequency channel protected forthe primary system may include one or more frequency channel allocatedfor the primary system and its adjacent frequency channels. In thepresent embodiment, the power allocation unit 140 switches the powerallocation methods between the first group of secondary systems of whichthe distance from the primary system is less than a prescribed distancethreshold value and the second group of secondary systems of which thedistance from the primary system is greater than the distance thresholdvalue. The distance of a secondary system from a primary system may be,for example, a distance from the center of the service area of theprimary system, or may be a distance from an outer edge of the servicearea or the guard area.

(Examples of Power Allocation Methods)

In this description, the following four methods are mainly explained aspower allocation methods performed by the power allocation unit 140.However, these are mere examples, and other power allocation methods maybe used.

(1) The first method: Fixed power allocation

(2) The second method: Considering path loss

(3) The third method: Considering accumulative interferences

(4) The fourth method: Considering interference between channels

(1) The first method

In the first method, for each secondary system, a fixed transmissionpower value or a transmission power value requested from the secondarysystem is allocated. The fixed transmission power value may be commonlydefined among all secondary systems, or may be defined for eachattribute such as a type and a class of a device. In this case, thecalculation cost required to calculate the transmission power issubstantially close to zero.

(2) The Second Method

In the second method, a larger transmission power value is allocated foreach secondary system as the path loss from the secondary system to theprimary system is greater. The calculation formula of the transmissionpower allocated for each secondary system may be, for example, thecalculation formula described in the above-described Patent Document 1.Other examples of the calculation formula are further provided later. Inthis case, the calculation cost required to calculate the transmissionpower is not zero, but is relatively small.

(3) The Third Method

In the third method, the transmission power is distributed to eachsecondary system so that an accumulative interference amount on the samechannel from plural secondary systems to a primary system does notexceed an acceptable interference amount of the primary system.

The third method may be, for example, a method based on the interferencecontrol model explained below. Note that here, formulas of theinterference control model are written by using the true valueexpression, but this interference control model can handle the decibelvalue expression by converting the formulas.

First, given that a reference point for the interference calculation isi, the frequency channel allocated for the primary system is f_(j), theacceptable interference amount of the primary system isI_(acceptable)(i, f_(j)). Additionally, assuming that a single secondarysystem k which secondarily uses the channel f_(j) is located on aperiphery of the guard area. Accordingly, a relation expression belowholds among a maximum transmission power P_(max)(f_(j), k) of thesecondary system, a path loss L(i, f_(j), k) for a minimum separationdistance (width of the guard area), and an acceptable interferenceamount I_(acceptable)(i, f_(j)).I _(acceptable)(i,f _(j))=P _(max)(f _(j) ,k)·L(i,f _(j) ,k)  (1)

Here, a position of the reference point is decided on the basis of theinformation the communication control device 100 receives from the dataserver 30 at step S11 in FIG. 4. In a case where the reference point isdefined in advance, the position data (e.g., longitude and latitude,etc.) representing the position of the relevant reference point may bereceived from the data server 30. Additionally, the communicationcontrol device 100 may use the position data of the node, service area,or guard area of the primary system received from the data server 30,and the position data received from each master node 200 to dynamicallydecide the position of the reference point.

When there are plural secondary systems of the same group that use thesame frequency channel, in the transmission power allocation for each ofthe secondary systems, the following relation expression (an evaluationformula of accumulative interference amount) obtained by expandingFormula (1) needs to be satisfied for each frequency channel.

$\begin{matrix}{{I_{acceptable}\left( {i,f_{j}} \right)} \geq {\sum\limits_{k = 1}^{M_{j}}{{P\left( {f_{j},k} \right)} \cdot {L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)}}}} & (2)\end{matrix}$

Here, a right-hand side in Formula (2) represents the sum ofinterference amounts caused by the secondary systems to whichsecondarily use a channel the same as the channel f_(j) allocated forthe primary system. M_(j) is the number of the secondary systems whichsecondarily use the same channel, P(f_(j), k) is a power allocated forthe k-th secondary system, L(i, f_(j), k) is a path loss between thek-th secondary system and the reference point i of the primary system,and G(f_(j), k) is a gain component. Note that the above M_(j) may bethe number of the active secondary systems (or master nodes).

In the third power allocation method, for each frequency channel, thepower allocation unit 140, after tentatively distributing thetransmission power to secondary systems that secondarily uses thefrequency channel, corrects the distributed transmission power so as tosatisfy the above evaluation formula of the accumulative interferenceamount.

The tentative distribution of the transmission power may be performed inaccordance with, for example, three types of methods including the fixedmargin method, the even method, and the uneven method that are explainedbelow. Note that the power distribution formulas in these methods may beused as the calculation formula of the transmission power for the secondpower allocation method.

(Fixed Margin Method)

A first method is a fixed margin method. In a case of the fixed marginmethod, a distribution margin MI (and safety margin SM) fixedly set inadvance is used to calculate the transmission power allocated to eachsecondary system. A transmission power P(f_(j), k) which is allocated tothe k-th secondary system to use the frequency channel f_(j) is derivedfrom a formula below.P(f _(j) ,k)=I _(acceptable)(i,f _(j))/L(i,f _(j) ,k)·G(f _(j),k)·MI·SM  (8)(Even Method)

A second method is an even method. In a case of the even method, thetransmission powers allocated to respective secondary systems are equalto each other. In other words, the transmission power is evenlydistributed to a plurality of secondary systems. The transmission powerP(f_(j), k) which is allocated to the k-th secondary system to use thefrequency channel f_(j) is derived from a formula below.

$\begin{matrix}{{P\left( {f_{j},k} \right)} = {{I_{acceptable}\left( {i,f_{j}} \right)}/{\sum\limits_{{bb} - 1}^{M_{j}}\left\{ {{L\left( {i,f_{j},{kk}} \right)} \cdot {G\left( {f_{j},{kk}} \right)}} \right\}}}} & (4)\end{matrix}$(Uneven Method)

A third method is an uneven method. In a case of the uneven method, thesecondary system has the larger distance to the primary system, thesecondary system is allocated with the more transmission power.Accordingly, chances of the secondary usage as a whole may be increased.The transmission power P(f_(j), k) allocated to the k-th secondarysystem to use the frequency channel f_(j) is derived from a formulabelow.P(f _(j) ,k)=I _(acceptable)(i,f _(j))/{L(i,f _(j) ,k)·G(f _(j) ,k)·M_(j)}  (5)

Moreover, the even method and the uneven method may be combined with aninterference-causing margin reduction method described below.

(Interference-Causing Margin Reduction Method)

The interference-causing margin reduction method is a method in whichthe safety margin SM for reducing an interference risk is counted, andmay be used in combination with the even method or uneven methoddescribed above. The transmission power P(f_(j), k) is derived fromFormula (6) below in terms of the combination with the even method, andFormula (7) below in terms of the combination with uneven method. Here,SM represents a safety margin set in advance or notified from the masternode 200.

$\begin{matrix}{{P\left( {f_{j},k} \right)} = {{I_{acceptable}\left( {i,f_{j}} \right)}/{\sum\limits_{{kk} = 1}^{M_{j}}\left\{ {{L\left( {i,f_{j},{kk}} \right)} \cdot {G\left( {f_{j},{kk}} \right)} \cdot {SM}} \right\}}}} & (6) \\{{P\left( {f_{j},k} \right)} = {{I_{acceptable}\left( {i,f_{j}} \right)}/\left\{ {{L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot M_{j} \cdot {SM}} \right\}}} & (7)\end{matrix}$

Further, the methods described above may be combined with a weighteddistribution method described below.

(Weighted Distribution Method)

The weighted distribution method is a method in which distribution ofthe transmission power is weighted depending on a priority for each thesecondary system. The transmission power P(f_(j), k) is derived fromFormula (8) below in terms of the combination with the even method, andFormula (9) below in terms of the combination with the uneven method. Inaddition, the transmission power P(f_(j), k) is derived from Formula(8′) below in terms of the combination with the even method andinterference-causing margin reduction method, and Formula (9′) below interms of the combination with the uneven method and interference-causingmargin reduction method. Here, w_(k) represents a weighting depending onthe priority. Note that a weight w_(j) for each frequency channel may beused in place of the weight w_(k) for each secondary system.

$\begin{matrix}{{P\left( {f_{j},k} \right)} = {\left( {w_{k}/{\sum\limits_{{kk} = 1}^{M_{j}}w_{kk}}} \right){{I_{acceptable}\left( {i,f_{j}} \right)}/{\sum\limits_{{kk} = 1}^{M_{j}}\left\{ {{L\left( {i,f_{j},{kk}} \right)} \cdot {G\left( {f_{j},{kk}} \right)}} \right\}}}}} & (8) \\{{P\left( {f_{j},k} \right)} = {\left( {w_{k}/{\sum\limits_{{kk} = 1}^{M_{j}}w_{kk}}} \right){{I_{acceptable}\left( {i,f_{j}} \right)}/\left\{ {{L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot M_{j}} \right\}}}} & (9) \\{{P\left( {f_{j},k} \right)} = {\left( {w_{k}/{\sum\limits_{{kk} = 1}^{M_{j}}w_{kk}}} \right){{I_{acceptable}\left( {i,f_{j}} \right)}/{\sum\limits_{{kk} = 1}^{M_{j}}\left\{ {{L\left( {i,f_{j},{kk}} \right)} \cdot {G\left( {f_{j},{kk}} \right)} \cdot {SM}} \right\}}}}} & \left( 8^{\prime} \right) \\{{P\left( {f_{j},k} \right)} = {\left( {w_{k}/{\sum\limits_{{kk} = 1}^{M_{j}}w_{kk}}} \right){{I_{acceptable}\left( {i,f_{j}} \right)}/\left\{ {{L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot M_{j} \cdot {SM}} \right\}}}} & \left( 9^{\prime} \right)\end{matrix}$

Here, in the primary system there may be some cases where only theacceptable interference amount I_(acceptable)(i, f_(jj)) of thefrequency channel f_(jj) is defined and the acceptable interferenceamount of the adjacent frequency channel f_(j) is not defined. Forexample, such a case may occur when the frequency channel f_(jj) is achannel allocated to the primary system, and the adjacent channel f_(j)thereof is a channel not used by the primary system but protected. Inthat case, a distribution formula for distributing the transmissionpower to the secondary systems which secondarily use the adjacentchannel f is derived by, in the distribution formulas described above,replacing the acceptable interference amount I_(acceptable)(i, f_(j))with the I_(acceptable)(i, f_(jj)) and replacing the term L(i,f_(j),k)·G(f_(j), k) of the path loss and gain component with a termL(i,f_(j),k)·G(f_(j), k)/H(f_(jj), k) for counting the loss component.As an example, a distribution formula in the fixed margin method may bemodified as below.P(f _(j) ,k)=I _(acceptable)(i,f _(jj))·H(f _(jj) ,f _(j) ,k)/L(i,f _(j),k)·G(f _(j) ,k)·MI·SM  (3′)

Next, the power allocation unit 140 searches in the service area of theprimary system for a point at which evaluation of the interferenceamount on the basis of the distributed transmission power is theharshest. For example, a point i′ at which the interference amount isthe harshest is searched as in the following Formula (10) or Formula(10′).

$\begin{matrix}{i^{\prime} = {\underset{i}{\arg\;\min}\left( {{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{k = 1}^{M_{j}}{{P\left( {f_{j},k} \right)} \cdot {L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)}}}} \right)}} & (10) \\{i^{\prime} = {\underset{i}{\arg\min}\left( {{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{k = 1}^{M_{j}}{{P\left( {f_{j},k} \right)} \cdot {L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot {SM}}}} \right)}} & \left( 10^{\prime} \right)\end{matrix}$

Next, the power allocation unit 140 calculates a correction coefficientΔ of power distribution as in the following formulas based on the totalinterference amount and the acceptable interference amountI_(acceptable)(i, f_(j)) at the point i′.

$\begin{matrix}{\Delta = \frac{I_{acceptable}\left( {i^{\prime},f_{j}} \right)}{\sum\limits_{k = 1}^{M_{j}}{{P\left( {f_{j},k} \right)} \cdot {L\left( {i^{\prime},f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)}}}} & (11) \\{\Delta = \frac{I_{acceptable}\left( {i^{\prime},f_{j}} \right)}{\sum\limits_{k = 1}^{M_{j}}{{P\left( {f_{j},k} \right)} \cdot {L\left( {i^{\prime},f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot {SM}}}} & \left( 11^{\prime} \right)\end{matrix}$

Note that the above Formula (11′) can be used when theinterference-causing margin reduction method is applied in powerdistribution.

Then, the power allocation unit 140 corrects the transmission power inaccordance with the following formula by using the calculated correctioncoefficient 4, and derives the acceptable transmission power P′(f_(j),k) of the secondary system k.P′(f _(j) ,k)=P(f _(j) ,k)·Δ  (12)(4) The Fourth Method

In the fourth method, the transmission power is distributed to each ofsecondary systems so that the sum of the accumulative interferenceamount on the same channel and the accumulative interference amountsbetween channels from plural secondary systems to a primary system doesnot exceed the acceptable interference amount of the primary system. Theevaluation formula of the accumulative interference amount in the fourthmethod may be the following formula that introduces the term of theinterference between channels into the right-hand side of the aboveFormula (2) in the third method.

$\begin{matrix}{{I_{acceptable}\left( {i,f_{j}} \right)} \geq {{\sum\limits_{k = 1}^{M_{j}}{{P\left( {f_{j},k} \right)} \cdot {L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)}}} + {\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\left\{ {{P\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot {{G\left( {f_{jj},{kk}} \right)}/{H\left( {f_{j},f_{jj},{kk}} \right)}}} \right\}}}}} & (13)\end{matrix}$

The second term on the right-hand side of Formula (13) represents thesum of the interference amount originating from the secondary systemswhich secondarily use a channel different from but adjacent to thechannel f_(j). O_(j) is the number of the adjacent channels, jj is anindex of the adjacent channels, N_(jj) is the number of secondarysystems that secondarily uses the adjacent channels, kk is an index ofthe secondary systems that secondarily uses the adjacent channels,H(f_(j), f_(jj), kk) is a loss component of the secondary system kk fromthe adjacent channels f_(jj) to the channel f_(j). Note that N_(jj) maybe a number of the active secondary systems (or master nodes).

The gain component G in Formula (13) can be determined mainly on thebasis of the causes shown in the following Table 1.

TABLE 1 FACTOR OF GAIN COMPONENT BETWEEN SYSTEMS SYMBOLS FACTOR PR(f_(jj)-f_(j)) Protection ratio between channels of which frequenciesare separated f_(jj)-f_(j) μσ Shadowing margin σ Shadowing (standarddeviation) D_(dir) (i, f_(j (or jj))) Signal identification degree ofantenna directionality in primary reception station at reference point iin channel f_(j) (or f_(jj)) D_(ool) (i, f_(j (or jj))) Signalidentification degree of polarization in primary reception station atreference point i in channel f_(j) (or f_(jj)) G_(ant) (i,f_(j (or jj))) Antenna gain in primary reception station at referencepoint i in channel f_(j)(or f_(jj)) L_(f) (i, f_(j (or jj))) Fader lossin primary reception station at reference point i in channel f_(j) (orf_(jj))

For example, regarding the protection ratio PR in Table 1, the followingidea can be applied. In other words, the acceptable interference amountto the primary system that uses a channel f_(BS) from the secondarysystem that secondarily uses a channel f_(CR) is I_(acceptable). Inaddition, a required reception power of the primary system isP_(req)(f_(BS)). The following formula is established between theseparameters.I _(acceptable) =P _(req)(f _(BS))/PR(f _(CR) −f _(BS))  (14)

Note that when the protection ratio is represented in the decibel valueexpression, the following formula can be used instead of the aboveFormula (14).I _(acceptable) =P _(req)(f _(BS))/10^(PR(f) ^(CR) ^(−f) ^(BS)^()/10)  (15)

The loss component H in Formula (13) depends, for example, onselectivity and leakage ratio of the adjacent channels. Note that theabove-provided Non-Patent Document 1 should be referenced for moredetails of these gain component and loss component.

In the fourth power allocation method, for each frequency channel, thepower allocation unit 140, after tentatively distributing thetransmission power to secondary systems that secondarily uses thefrequency channel, redistributes the tentatively distributedtransmission power in consideration of the effect of the interferencebetween channels. The power allocation unit 140, then, corrects theredistributed transmission power so as to satisfy the above evaluationformula.

More specifically, the power allocation unit 140, firstly, tentativelydistributes the transmission power to each frequency channel that isused by the secondary systems in accordance with any method (e.g.,Formulas (3)-(9′)) explained in relation to the third power allocationmethod. Moreover, the power allocation unit 140 counts the interferencebetween channels in and redistributes the transmission power among thesecondary systems. For example, redistribution of the transmission powerwith the even method can be performed in accordance with the followingFormula (16) (Formula (16′) in the case of a combination with theinterference-causing margin reduction method).

$\begin{matrix}{{P^{\prime}\left( {f_{j},k} \right)} = \frac{{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\begin{matrix}\left\{ {{P\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot} \right. \\\left. {{G\left( {f_{jj},{kk}} \right)}/{H\left( {f_{j},f_{jj},{kk}} \right)}} \right\}\end{matrix}}}}{\sum\limits_{{kk} = 1}^{M_{j}}\left\{ {{L\left( {i,f_{j},{kk}} \right)} \cdot {G\left( {f_{j},{kk}} \right)}} \right\}}} & (16) \\{{P^{\prime}\left( {f_{j},k} \right)} = \frac{{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\begin{matrix}\left\{ {{P\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot} \right. \\\left. {{G\left( {f_{jj},{kk}} \right)}/{H\left( {f_{j},f_{jj},{kk}} \right)}} \right\}\end{matrix}}}}{\sum\limits_{{kk} = 1}^{M_{j}}\left\{ {{L\left( {i,f_{j},{kk}} \right)} \cdot {G\left( {f_{j},{kk}} \right)} \cdot {SM}} \right\}}} & \left( 16^{\prime} \right)\end{matrix}$

Formula (16) indicates that after the interference amount originatingfrom the use of adjacent channels is subtracted from the acceptableinterference amount of the primary system, the remaining acceptableinterference amount is redistributed among the remaining secondarysystems. Similarly, redistribution of the transmission power with theuneven method can be performed in accordance with the following Formula(17) (Formula (17′) in the case of a combination with theinterference-causing margin reduction method).

$\begin{matrix}{{P^{\prime}\left( {f_{j},k} \right)} = \frac{{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\begin{matrix}\left\{ {{P\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot} \right. \\\left. {{G\left( {f_{jj},{kk}} \right)}/{H\left( {f_{j},f_{jj},{kk}} \right)}} \right\}\end{matrix}}}}{{L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot M_{j}}} & (17) \\{{P^{\prime}\left( {f_{j},k} \right)} = \frac{{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\begin{matrix}\left\{ {{P\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot} \right. \\\left. {{G\left( {f_{jj},{kk}} \right)}/{H\left( {f_{j},f_{jj},{kk}} \right)}} \right\}\end{matrix}}}}{{L\left( {i,f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot M_{j} \cdot {SM}}} & \left( 17^{\prime} \right)\end{matrix}$

Note that, as a matter of course, weight in the weighted distributionmethod may be further applied to each of the above-provided formulas forredistribution.

Next, the power allocation unit 140 searches for a point at whichevaluation of the interference amount based on the redistributedtransmission power is the harshest in the service area of the primarysystem. For example, a point i′ at which the interference amount is theharshest is searched as in the following Formula (18) or Formula (18′).

$\begin{matrix}{i^{\prime} = {\underset{i}{\arg\;\min}\begin{pmatrix}{{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{k = 1}^{M_{j}}{{{P^{\prime}\left( {f_{j},k} \right)} \cdot {L\left( {i,f_{j},k} \right)} \cdot G}\left( {f_{j},k} \right)}} -} \\{\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\left\{ {{P^{\prime}\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot {{G\left( {f_{jj},{kk}} \right)}/{H\left( {f_{j},{kk}} \right)}}} \right\}}}\end{pmatrix}}} & (18) \\{i^{\prime} = {\underset{i}{{\arg\min}\quad}\left( \left. \quad\begin{matrix}\begin{matrix}{{I_{acceptable}\left( {i,f_{j}} \right)} - {\sum\limits_{k = 1}^{M_{j}}{{P^{\prime}\left( {f_{j},k} \right)} \cdot}}} \\{{L{\left( {i,f_{j},k} \right) \cdot {G\left( {f_{j},k} \right)} \cdot {SM}}} -}\end{matrix} \\{\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\left\{ {{P^{\prime}\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i,f_{jj},{kk}} \right)} \cdot {G\left( {f_{jj},{kk}} \right)} \cdot {{SM}/{H\left( {f_{j},{kk}} \right)}}} \right\}}}\end{matrix} \right) \right.}} & \left( 18^{\prime} \right)\end{matrix}$

Next, the power allocation unit 140 calculates a correction coefficientΔ of power distribution as in the following formulas based on the totalinterference amount and the acceptable interference amountI_(acceptable)(i, f_(j)) at the point i′.

$\begin{matrix}{\Delta = \frac{I_{acceptable}\left( {i^{\prime},f_{j}} \right)}{\begin{matrix}{{\sum\limits_{k = 1}^{M_{j}}{{{P^{\prime}\left( {f_{j},k} \right)} \cdot {L\left( {i^{\prime},f_{j},k} \right)} \cdot G}\left( {f_{j},k} \right)}} +} \\{\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\left\{ {{{P^{\prime}\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i^{\prime},f_{jj},{kk}} \right)} \cdot {{G\left( {f_{jj},{kk}} \right)}/H}}\left( {f_{j},f_{jj},{kk}} \right)} \right\}}}\end{matrix}}} & (19) \\{\Delta = \frac{I_{acceptable}\left( {i^{\prime},f_{j}} \right)}{\begin{matrix}{{\sum\limits_{k = 1}^{M_{j}}{{P^{\prime}\left( {f_{j},k} \right)} \cdot {L\left( {i^{\prime},f_{j},k} \right)} \cdot {G\left( {f_{j},k} \right)} \cdot {SM}}} +} \\{\sum\limits_{{jj} = 1}^{O_{j}}{\sum\limits_{{kk} = 1}^{N_{jj}}\left\{ {{{P^{\prime}\left( {f_{jj},{kk}} \right)} \cdot {L\left( {i^{\prime},f_{jj},{kk}} \right)} \cdot {G\left( {f_{jj},{kk}} \right)} \cdot {{SM}/H}}\left( {f_{j},f_{jj},{kk}} \right)} \right\}}}\end{matrix}}} & \left( 19^{\prime} \right)\end{matrix}$

Note that the above Formula (19′) can be used when theinterference-causing margin reduction method is applied in powerdistribution.

Then, the power allocation unit 140 corrects the transmission power inaccordance with the following formula by using the calculated correctioncoefficient 4, and derives the acceptable transmission power P″(f_(j),k) of the secondary system k.P″(f _(j) ,k)=P′(f _(j) ,k)·Δ  (20)(Combination of Power Allocation Methods)

The power allocation unit 140 may, for example, apply any one of theabove second to the fourth power allocation methods to a group ofsecondary systems of which a distance from a primary system is less thana distance threshold value and may apply the above first method to theother secondary systems. In addition, the power allocation unit 140 mayapply the above third or fourth method to the group of secondary systemsof which the distance from the primary system is less than a distancethreshold value and may apply the above first or second method to theother secondary systems. Furthermore, the power allocation unit 140 mayapply the above fourth method to the group of secondary systems of whichthe distance from the primary system is less than a distance thresholdvalue and may apply one of the above first to third power allocationmethods to the other secondary systems. The following table shows anexample of combinations of power allocation methods that can be appliedto each of the two groups of the secondary systems. Combinations markedwith circles in the table can be selected by the power allocation unit140.

TABLE 2 EXAMPLES OF COMBINATIONS OF APPLICABLE POWER ALLOCATION METHODSPOWER GROUP OF CLOSER SS ALLOCATION SECOND THIRD FOURTH METHOD FIRSTMETHOD METHOD METHOD METHOD GROUP OF FIRST ◯ ◯ ◯ MORE METHOD DISTANT SSSECOND ◯ ◯ METHOD THIRD ◯ METHOD FOURTH METHOD

As in the third and the fourth power allocation methods, when the powerallocation method based on the acceptable interference amount is appliedto each of groups, the acceptable interference amount may be distributedto each of the groups in accordance with a distance or path loss betweena reference point and a representative system of each group. Thereference point used to distribute the acceptable interference amountamong groups may be defined in advance or may be dynamically determinedin accordance with the positions of the secondary systems.

Note that in the above-described third power allocation method, thecorrection of the acceptable transmission power in Formula (10) toFormula (12) may be omitted. Similarly, in the above-described fourthpower allocation method, the correction of the acceptable transmissionpower in Formula (18) to Formula (20) may be omitted. As a powerallocation method separate from the third and fourth power allocationmethods, a method in which these corrections of the acceptabletransmission power are omitted may be employed and such a method may beapplied to a group closer to the primary system or to a group moredistant from the primary system.

Moreover, the power allocation unit 140 may divide the secondary systemsinto three or more groups by using plural distance threshold values, andfor each of the three or more groups, different power allocation methodsmay be selected. The distance threshold value used by the powerallocation unit 140 may be defined in a fixed manner. Alternatively, thedistance threshold value may be dynamically set in accordance withparameters such as conditions of the primary system (e.g., the size ofthe service area, the position of the primary reception station, or thenumber of primary reception stations) or the number of secondarysystems.

The power allocation unit 140 calculates the value of the transmissionpower allocated for each of the secondary system in this manner with themethod selected in accordance with the distance from the primary system,and notifies each of the secondary systems of the calculatedtransmission power value via the communication unit 110.

[2-2. Flow of Process]

Next, by using FIG. 6, a flow of process performed by the communicationcontrol device 100 according to the present embodiment is explained.FIG. 6 is a flowchart illustrating an example of a flow of a powerallocation process performed by the communication control device 100.Here, as an example, the secondary systems are grouped into two groupsby using one distance threshold value.

With reference to FIG. 6, the power allocation unit 140, firstly,obtains information on the primary system provided from the data server30 (step S110). The power allocation unit 140 also obtains informationon the secondary system collected from the master node 200 (step S120).Next, the power allocation unit 140 repeats processes in steps S132 toS138 for each of target secondary systems for which power is allocated(step S130).

In the repeating process for each secondary system, the power allocationunit 140 calculates a distance from the primary system to the targetsecondary system (step S132). Next, the power allocation unit 140compares the calculated distance with a prescribed distance thresholdvalue (step S134). Here, when the distance from the primary system tothe target secondary system is less than the distance threshold value,the power allocation unit 140 classifies the target secondary systeminto the first group (step S136). Meanwhile, when the distance from theprimary system to the target secondary system does not exceed thedistance threshold value, the power allocation unit 140 classifies thetarget secondary system into the second group (S138).

When the classification of the secondary systems is completed, the powerallocation unit 140 calculates the transmission power allocated for thesecondary systems that belong to the first group with a method with agreater computational cost (step S140). The power allocation methodselected here may be any one of the above-described second to fourthmethods.

In addition, the power allocation unit 140 calculates (or determines)the transmission power allocated for the secondary system that belongsto the second group with a method with a computational cost lower thanthat of the method selected in step S140 (step S150). The powerallocation method selected here may be any one of the above-describedfirst to third methods.

The power allocation unit 140, then, notifies the master node 200 of thesecondary systems of the transmission power value calculated in stepsS140 and S150 via the communication unit 110 (step S160). Note that thenotification of step S160 in FIG. 6 can be equivalent to thetransmission of a power notification message in step S17. For thesecondary system of which the allocated transmission power is notupdated from the value that has been notified, the notification of thetransmission power value may be omitted.

3. EXEMPLARY CONFIGURATION OF MASTER NODE

FIG. 7 is a block diagram illustrating an example of a configuration ofa master node 200 that is a communication device operating the secondarysystem by using the transmission power allocated by the above-describedcommunication control device 100. With reference to FIG. 7, the masternode 200 is provided with a communication unit 210, a control unit 220,a storage unit 230, and a wireless communication unit 240.

The communication unit 210 operates as a communication interface forcommunication between the data server 30 and the communication controldevice 100 by the master node 200. The communication unit 210, under acontrol by the control unit 220, transmits information on the secondarysystem to the data server 30, for example, at the start of the secondaryusage. Additionally, the communication unit 210 receives informationnotified from the data server 30. Moreover, the communication unit 210transmits and receives a request for power allocation and acknowledge toand from the communication control device 100. Further, thecommunication unit 210 receives the power notification message from thecommunication control device 100 to output the received message to thecontrol unit 220.

The control unit 220 corresponds to a processor such as CPU or DSP. Thecontrol unit 220 operates various functions of the master node 200 byexecuting programs stored in the storage unit 230 or other storagemedia. For example, the control unit 220 suppresses the interference tothe primary system at the time of secondary system operation bycooperating with the communication control device 100 in accordance withthe sequence exemplified in FIG. 4. More specifically, the control unit220 sets the transmission power within a range of the transmission powerallocated to the master node 200 (or the secondary system operated bythe master node 200), which is notified from the communication controldevice 100, to the wireless communication unit 240. The control unit 220may, for example, distribute the allocated transmission power amongnodes that participate in the secondary system.

The storage unit 230 uses a storage medium such as a hard disk orsemiconductor memory to store a program and data used for cooperationwith the communication control device 100 and operation of the secondarysystem.

The wireless communication unit 240 operates as a wireless communicationinterface for wireless communication between the master node 200 and theslave nodes connected with the relevant master node 200. The wirelesscommunication unit 240 transmits and receives a wireless signal to andfrom one or more slave nodes in accordance with IEEE802.22,IEEE802.11af, or ECMA-392, for example. The transmission power of thewireless signal transmitted by the wireless communication unit 240 maybe controlled within the above described range of the allocabletransmission power by the control unit 220.

4. CONCLUSION

Up to this point, an embodiment of a technology according to the presentdisclosure is explained in detail by using FIG. 1 to FIG. 7. Accordingto the above-described embodiment, when transmission power is allocatedfor a secondary system that secondarily uses a frequency channelprotected for a primary system, power allocation methods are switchedbetween the first group of secondary systems of which a distance fromthe primary system is less than a prescribed threshold and the secondgroup of secondary systems of which the distance from the primary systemexceeds the threshold. Accordingly, for secondary systems that arelocated farther from the primary system, calculation load for powerallocation can be suppressed by employing a simple power allocationmethod with low computational cost. In addition, even if thetransmission power is allocated with a simple method for the secondarysystems that are located far in the distance and cause only a low levelinterference, detrimental effects on the primary system can beprevented.

According to the above-described embodiment, the simple power allocationmethod may be, for example, a method that does not depend on path losson a path from a secondary system to a primary system. In this case, forthe secondary systems that are located farther away, the transmissionpower to be allocated for the secondary system can be determined withoutsubstantial calculation load. Moreover, the simple power allocationmethod may be a method that does not take an accumulative interferenceto the primary system into consideration. In this case, for thesecondary systems that are located farther away, the transmission powercan be easily allocated independently with a calculation for eachsecondary system. Furthermore, the simple power allocation method may bea method that does not take an interference from the secondary system tothe primary system between channels into consideration. In this case,for the secondary systems that are located farther away, thetransmission power can be distributed independently for each frequencychannel

Note that a series of control processes by the respective devicesexplained in this description may be achieved by any of software,hardware, and combination of software and hardware. Programsconstituting the software are stored in a storage medium provided insideor outside each device in advance, for example. Then, each program is,for example, read into a RAM (Random Access Memory) when executed to beexecuted by a processor such as a CPU (Central Processing Unit).

In the above descriptions, preferred embodiments of the presentdisclosure are described in detail with reference to the appendeddrawings, but the technical scope of the present disclosure is notlimited to these examples. It is apparent for those who have ordinaryknowledge in the technical field of the present disclosure to arriveideas of various modification examples or correction examples within thescope of technical ideas described in the claims, and such modificationexamples and correction examples are also construed as pertaining to thetechnical scope of the present disclosure.

Additionally, the present technology may also be configured as below.

(1) A communication control device including

a power allocation unit configured to allocate transmission power forsecondary use of a frequency channel protected for a primary system to asecondary system,

wherein the power allocation unit switches power allocation methodsbetween a first group of secondary systems of which a distance from theprimary system is less than a prescribed threshold and a second group ofsecondary systems of which a distance from the primary system exceedsthe prescribed threshold.

(2) The communication control device according to (1),

wherein a power allocation method selected for the first group is amethod that depends on a path loss regarding each secondary system, and

wherein a power allocation method selected for the second group is amethod that does not depend on a path loss regarding each secondarysystem.

(3) The communication control device according to (1),

wherein a power allocation method selected for the first group is amethod that considers accumulative interferences from a plurality ofsecondary systems to the primary system, and

wherein a power allocation method selected for the second group is amethod that does not consider accumulative interferences from aplurality of secondary systems to the primary system.

(4) The communication control device according to (1),

wherein a power allocation method selected for the first group is amethod that considers both an interference from a secondary system tothe primary system on a same channel and an interference betweenchannels, and

wherein a power allocation method selected for the second group is amethod that does not consider the interference from a secondary systemto the primary system between channels.

(5) The communication control device according to any one of (2) to (4),

wherein the power allocation method selected for the second group is amethod to allocate a fixed value or a value requested from eachsecondary system as a transmission power value to each secondary system.

(6) The communication control device according to (3) or (4),

wherein the power allocation method selected for the second group is amethod to allocate, to the secondary system, a larger transmission powervalue as a path loss from each secondary system to the primary systembecomes larger.

(7) The communication control device according to (4),

wherein the power allocation method selected for the second group is amethod to distribute transmission power into each secondary system sothat an accumulative interference amount on a same channel from aplurality of secondary systems to the primary system does not exceed anacceptable interference amount of the primary system.

(8) The communication control device according to any one of (2) to (4),

wherein the power allocation method selected for the first group is amethod to distribute transmission power to each secondary system so thata sum of an accumulative interference amount on a same channel from aplurality of secondary systems to the primary system and an accumulativeinterference amount between channels does not exceed an acceptableinterference amount of the primary system.

(9) The communication control device according to (2) or (3),

wherein the power allocation method selected for the first group is amethod to distribute transmission power into each secondary system sothat an accumulative interference amount on a same channel from aplurality of secondary systems to the primary system does not exceed anacceptable interference amount of the primary system.

(10) The communication control device according to (2),

wherein the power allocation method selected for the first group is amethod to allocate, to the secondary system, a larger transmission powervalue as a path loss from each secondary system to the primary systembecomes larger.

(11) A method for allocating transmission power for secondary use of afrequency channel protected for a primary system to a secondary system,the method including:

obtaining a distance to the secondary system from the primary system;

allocating transmission power to the secondary system with the firstpower allocation method when the obtained distance is less than aprescribed threshold; and

allocating transmission power to the secondary system with the secondpower allocation method that requires calculation cost lower than thatof the first power allocation method when the obtained distance exceedsthe prescribed threshold.

(12) A program for causing a computer of a communication control deviceto function as

a power allocation unit to allocate transmission power for secondary useof a frequency channel protected for a primary system to a secondarysystem,

wherein the power allocation unit switches power allocation methodsbetween a first group of secondary systems of which a distance from theprimary system is less than a prescribed threshold and a second group ofsecondary systems of which a distance from the primary system exceedsthe prescribed threshold.

REFERENCE SIGNS LIST

-   1 communication control system-   10 primary transmission station-   20 primary reception station-   100 communication control device-   140 power allocation unit-   200 master node of secondary system

What is claimed is:
 1. A communication control device comprising a powerallocation unit configured to: obtain information on a primary systemfrom a server; obtain information on a secondary system; calculate adistance of the secondary system from the primary system based on theobtained information; classify the secondary system into a first groupof which the distance from the primary systems is less than a prescribedthreshold and a second group of which the distance from the primarysystem exceeds the prescribed threshold; allocate a transmission powerto the first group with a first power allocation method; and allocate atransmission power to the second group with a second power allocationmethod, wherein the first power allocation method has a greatercomputational cost than that of the second power allocation method. 2.The communication control device according to claim 1, wherein the firstpower allocation method is a method that depends on a path lossregarding each secondary system, and wherein the second power allocationmethod is a method that does not depend on a path loss regarding eachsecondary system.
 3. The communication control device according to claim2, wherein the second power allocation method is a method to allocate afixed value or a value requested from each secondary system as atransmission power value to each secondary system.
 4. The communicationcontrol device according to claim 2, wherein the second power allocationmethod is a method to distribute transmission power to each secondarysystem so that a sum of an accumulative interference amount on a samechannel from a plurality of secondary systems to the primary system andan accumulative interference amount between channels does not exceed anacceptable interference amount of the primary system.
 5. Thecommunication control device according to claim 2, wherein the firstpower allocation method is a method to distribute transmission powerinto each secondary system so that an accumulative interference amounton a same channel from a plurality of secondary systems to the primarysystem does not exceed an acceptable interference amount of the primarysystem.
 6. The communication control device according to claim 2,wherein the first power allocation method is a method to allocate, tothe secondary system, a larger transmission power value as a path lossfrom each secondary system to the primary system becomes larger.
 7. Thecommunication control device according to claim 1, wherein the firstpower allocation method is a method that considers accumulativeinterferences from a plurality of secondary systems to the primarysystem, and wherein the second power allocation method is a method thatdoes not consider accumulative interferences from a plurality ofsecondary systems to the primary system.
 8. The communication controldevice according to claim 7, wherein the second power allocation methodis a method to allocate, to the secondary system, a larger transmissionpower value as a path loss from each secondary system to the primarysystem becomes larger.
 9. The communication control device according toclaim 1, wherein the first power allocation method is a method thatconsiders both an interference from a secondary system to the primarysystem on a same channel and an interference between channels, andwherein the second power allocation method is a method that does notconsider the interference from a secondary system to the primary systembetween channels.
 10. The communication control device according toclaim 9, wherein the second power allocation method is a method todistribute transmission power into each secondary system so that anaccumulative interference amount on a same channel from a plurality ofsecondary systems to the primary system does not exceed an acceptableinterference amount of the primary system.
 11. A method for allocatingtransmission power for secondary use of a frequency channel protectedfor a primary system to a secondary system, the method comprising:obtaining information on a primary system from a server; obtaininginformation on a secondary system; calculating a distance of thesecondary system from the primary system based on the obtainedinformation; classifying the secondary system into a first group ofwhich the distance from the primary systems is less than a prescribedthreshold and a second group of which the distance from the primarysystem exceeds the prescribed threshold; allocating a transmission powerto the first group with a first power allocation method; and allocatinga transmission power to the second group with a second power allocationmethod, wherein the first power allocation method has a greatercomputational cost than that of the second power allocation method. 12.A computer readable medium on which a program is stored for causing acomputer of a communication control device to function as a powerallocation unit configured to: obtain information on a primary systemfrom a server; obtain information on a secondary system; calculate adistance of the secondary system from the primary system based on theobtained information; classify the secondary system into a first groupof which the distance from the primary systems is less than a prescribedthreshold and a second group of which the distance from the primarysystem exceeds the prescribed threshold; allocate a transmission powerto the first group with a first power allocation method; and allocate atransmission power to the second group with a second power allocationmethod, wherein the first power allocation method has a greatercomputational cost than that of the second power allocation method.